The CREB (cAMP-response element binding) transcription factor is a stimulus-induced phospho-protein that is involved in numerous cell signaling pathways. Dysfunction and deregulation of CREB and CREB- interacting proteins cause human diseases such as cancer and neurodegeneration. CREB appears to play a key role in cell defense and survival in various tissues;however, the mechanisms through which CREB is involved in cell survival and the reason why deregulation of CREB function causes these human diseases remain incompletely understood. CREB phosphorylation at Ser-133 is the major posttranslational modification that enhances CREB activity in response to receptor-coupled stimuli. However, the status of CREB Ser-133 phosphorylation was not always correlated with CREB transcription function, suggesting that another event along with CREB Ser-133 phosphorylation seems to be involved in CREB regulation in a stimulus-specific manner. This research project may provide evidence and a critical answer to these unsolved problems because we recently found that HIPK2 (homeodomain interacting protein kinase 2), a genotoxic stress responsive kinase, activates CREB via phosphorylation of a new serine site (Ser-271) but not Ser-133, resulting in activation of CREB transcription function. We will test our hypothesis that HIPK2 is a new regulator of the CREB transcription factor via phosphorylation of this new CREB site that induces a cell survival program in genotoxic and oxidative stress conditions. The proposed experiments will focus on characterization of molecular mechanism through which CREB phosphorylation by HIPK2 activates its transcription function as well as downstream events including expression of target genes and cellular susceptibility to genotoxic stress in in vitro and in vivo models. The scientific impact of this research will be broad and significant because CREB regulates essential cellular events such as cell growth, differentiation, metabolism, and immune response. Therefore the unveiled new CREB regulation from successful completion of this proposal will enhance our understanding in various physiological and disease conditions closely associated with the CREB activity. PUBLIC HEALTH RELEVANCE: Genotoxic and oxidative stress induced by environmental and manmade chemicals are associated with human disease including cancer and neurodegeneration (such as Alzheimer and Parkinson's diseases), and aging;therefore, research to determine cellular defense mechanisms against the harmful stress is important for our understanding of the pathogenesis, prevention, and/or delay of these diseases. CREB is an essential transcription factor that plays critical roles in cell metabolism, differentiation, survival, and proliferation in various cell types. Indeed, accumulating evidence indicates that dysfunction and deregulation of CREB cause cancer and neuronal cell damage. CREB is involved in cell survival in genotoxic stress conditions;however, in contrast to intensive characterization of CREB in external stimuli that exert long-term effects such as cell differentiation and proliferation, molecular mechanisms behind CREB regulation in detrimental genotoxic and oxidative stress conditions remain largely unknown. This proposal will characterize a novel CREB regulatory pathway and mechanism we recently found, which are different from of a previously known CREB pathway. We anticipate that successful completion of proposed experiments will improve our understanding of how cells elicit CREB-regulated cell survival program against these stress and disease conditions. The impact of this research will be broad and significant in many research areas because the CREB transcription factor regulates numerous cellular functions in various types of tissues. Innovation of this research will include demonstration of a novel CREB signaling pathway and downstream target genes involved in stress response in cellular levels and an animal model.